how to turn off dividerand function?

when we are working with NN,the input data will be automatically divided into trn/val/tst subsets.how to turn off this function.I already set

net.divideFcn = 'dividetrain';

but i got error ="divideFcn" cannot be set to non-existing function "dividetrain".

if i plan to use cross validation, do i need to turn off this function to default?

thanks.

[Greg Heath]

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